Process of and apparatus for preserving and drying timber and other material.



G. B. & G. W. McMULLEN. 6.3. II E. w. McMULLEN, exzcurons or e. w. McMULLEN,'DEC'D. PROCESS OF AND APPARATUS FOR PRESERVING AND DRYING TIMBER AND OTHER MATERIAL.

APPLICATION FILED SEPT- I-9I6.

Patented Sept. 3, 1918.

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GEORGE B. MOMULLEN, 0F PICTON, ONTARIO, CANADA, AND GEORGE MGMULLEN,

DECEASED, LATE 0F PICTON, ONTARIO, CANADA, BY GEORGE PIGTON, CANADA, AND EARL W. MOMULLEN, EXECUTORS.

B. MCMULLEN, or

PROCESS OF AND APPARATUS FOR PRESERVING AND DRYTNGi '.I I.'LV.IIBER ANDv OTHER MATERIAL.

Specification of Letters Patent.

Application filed September 1, 1916. Serial No. 118,134.

To all whom it may concern:

Be it known thatil, GEORGE B. MCMULLEN, a subject of theKing of Great Britain, and resident of Picton, in the Province of Ontario, Canada, (whdse post-oflice address is Picton, Province of Ontario, Canada,) and Gnoncn W. MOMULLEN, deceased, formerly of Picton, in the Province of Ontario, Canada, have invented certain new and useful Improvements in Processes of and Apparatus for Preserving and Drying Timber and other Material, set forth in the annexed specification.

Our present invention is an improvement on that described in our Patent No. 1,125,862, patented Jan. 19, 1915, in which we have fully described the conditions required for the preservation and complete drying of bulky pieces of timber, such as balks, beams,

railroad ties, telegraph poles, etc., without ment of a circulation or continuous flow of.

a volume of air or other gas over the material to be dried and our invention relates to improvements on this known mode of procedure, by which are attained distinctly new and advantageous results in economy of time and fuel, as well as a thoroughly .dried product.

Our invention includes the provision at some point in the circuit of rapidly-flowing air or gas, of an exit for moisture-laden air, and at another suitable point, of means for supplying additional air or gas to take the place of that which has been exhausted, the additional gas introduced into the circulating system bein drier than that which is removed, the ObJQCt being to furnish an additional supplyof gas which will be capable of taking up further quantities of moisture from the material being dried. This additional gas may be at the temperature of the outside air or may be heated to the temperature prevailing in the kiln the essential feature being that this additional gas shall have less moisture-content than that which is withdrawn from the kiln. We further provide a number :of separate means for controlling the conditions existing in the kiln, and thus enable; the drying operation Patented se t. 3, @918.

to be conducted in accordance with there quirements (such aerate of, drying of thematerial, temperature and relative humid- I ity) as they may arise at any particular time. Thus. the quantity. of moist air or gas drawn from the kiln is under control by means of a valve or damper in the exit pipe. The quantity of drier air or'gas introduced is under control by the valve in the entrance pipe. The rapidity of the circulating flow is under control, asthe speed of the fan may be varied. The humidity within the kiln can be exactly regulated by means provided for additional humidification in case the quantity ofmoisture being extracted from the material is not suiiicient to saturate the atmosphere to the desired extent. By means of thermometers and hygrometers, located at various positions through the kiln, the exact conditions of temperature and relative humidity are always ascertainable; and by the use of test blocks at various points in the kiln, the rate at which the drying is progressin is indicated.

The umidity is maintained during the drying stage of the operation, at such a some difierence, otherwise there would be nothing to promote the passage of moisture to the surface, but if there is much difference, checking will take place and the outside pores are liable to close, greatly retarding the drying operation. It will be evident that the result of this treatment is a very uniform reduction of moisture throughout the entire body of the timber and that the rate of drying depends on the speed with which the moisture can equalize throughout the timber. We have found in practice that this uniform reduction of moisture throughout the entire stick actually takes place. Railway ties cut in two, at the different stages in the process of drying, showed that in many cases the center was the first place to dry and that portions at some plistapce from the center were noticeably molst after the center was thoroughly dried. It is of vital importance that too high a temperature be avoided. By the use of higher temperatures than those used in our process, the drying may be effected more rapidly but only by impairing the strength of the tim her. The use of these higher temperatures appears to result not only in a chemical change in the Wood which lessens its strength, but also to cause a break-down of the pore-walls or fibers, which, while it facilitates the passage of moisture from the interior of the wood to the surface, at the same time injuriously affects its strength.

Our invention, permits the use of lower and safer temperatures, while providing such facilities for circulation and control that relatively rapid drying without injury to the wood is obtained.

We have found that as the drying progresses, the relative humidity may be lowered with safety and the drying thus accelerated.

Further, by our method the fuel cost is reduced to a minimum, since there is not and need not be any wasteful condensation within the body of the kiln itself, the removal of a portion of the warm moistureladen air in the kiln providing for the removal of the necessary percentage of moisture without allowing the escape of any surplus of heated air; and there is no heating of cooled air from a condenser or of any large quantity of outside air. The temperature of the kiln is easily and economically maintained at a uniform point, either by the provision of heating coils or other heating means within the kiln itself or by the heat imparted to the additional air sent into the kiln from the outside.

The process herein described has been found to be applicable not only to bulky pieces of wood, but also to thin lumber or small stuff like shoe-last blocks, etc.

Other objects of the invention will appear from "the accompanying specification and claims.

A suitable kiln for carrying out our invention is disclosed in the accompanying drawing, in which Figure 1 is a more or less diagrammatic illustration of the kiln; and Figs. 2 and 3 are respectively plan and elevation of a form of separator.

Referring to the drawings. 1 is a kiln having walls, preferably provided with insulating air spaces. the kiln being preferably arranged so that it can be sealed airtight. 9;. '2 are crossbar supports for the ties. the ties being preferably arranged in an upright position and spaced apart by galvanized iron strips 3. These strips may be provided with points 4: punched out of the strips to assist in maintaining them in place. The cross-bars 2, 2 are of less thickness than the ties and are arranged so that there will be free air passages between them. As the ties are spaced apart, there will be passages for the air or gas extending upwardly between the ties so that the air or gas comes into free contact with the surfaces of the ties while the free flow of gas is as uninterrupted as possible.

Beneath the cross-bar supports is a steam coil 7 for heating the air or gas. 8 is an open-top pan containing water and having within it steam heating pipes 9 to vaporize the water. 10 is a valved pipe, through which steam can be injected when desired. 11 is a pipe or series of pipes, at the top of the kiln, into which the air-or gas enters and is withdrawn from the kiln. 12 is an exit flue for hot moist air provided with a valve or damper 13. 14 is a down-take flue connected to pipe 11 and leading to the intake .of a fan 15 from which the air or gas is returned to the bottom of the kiln through the fine 16. Surrounding the down-take pipe 14 is a chamber 17 into the upper portion of which enters a valved fine 18, through which air or gas is admitted from the air or gas heater 20. 19 is a valved pipe, connected to the outer air, through which air at outside temperature may be admitted, the pipe 14 being provided with openings 21. A valved pipe 22 enables formaldehyde or other disinfectant to be introduced into the kiln. The mode of operation is as follows Thetimber, railway ties for example, is piled, whenever possible, on end. The drying of such bulky pieces, particularly where the bark is left on the sides of the ties. is efiected mainly through the cut faces, which by this arrangement are fully exposed to the rapidly flowing current of air or gas.

When the kiln has been filled. it is tightly closed, the valves or dampers 23 and 24- being also closed, and steam is turned into the coils 9 submerged in water in the pan 8 and a rapid production of vapor follows, the atmosphere of thekiln being quickly saturated.

Steam is also turned into the heating coils 7 and the heat from these coils, to gether with that of the vapor from the water pan gradually raises the temperature to the point desired. about 155 F. The timber is kept in this highly saturated. stagnant atmosphere until it is thoroughly heated through and the pores well opened, this preliminary period lasting. according to the size of the pieces and the character of the wood, from 24 to 72 hours or even longer with very large pieces.

The fan is then started and is run continuously throughout the remainder of the process. At the same time the relative humidity is lowered to between 90% and 95% ture-laden air or 13. The exhausted air is replaced what on the nature of and hardwood somewhat longer.

During the entire period of drying, the,

wood, under the influence of the maintained heat, is gradually giving up its moisturecontent in the form of vapor which is absorbed to the extent permitted by the rapid current of air or gas flowing over the surface of the wood. The desired percentage of moisture is continuously removed from the system by permitting some of the moisgas to escape through the exit flue 12, this amount being carefully controlled by means of the valve or damper by fresh drier air or gas admitted through pipe 18 from the heater or by air admitted through pipe 19 directly from the outer air. This outer unheated air is used mainly for regulating purposes, as when through carelessness of the operator or other cause, the temperature has risen higher than is desirable. In case the temperature has been permitted to fall too low, it can be quickly raised to the, desired degree by opening valy e 23, for instance (valve 24E being of course closed), thereby at once admitting into the circulating system a volume of heated air. So also the desired conditions of humidity can readily be maintained, since the supply of moisture can be quickly increased by the admission of live steam through pipe 10, and the relative humidity can be quickly decreased by admitting drier air, either cold or hot. 4

In order to provide for a rapid and uniform passage of the air or gas over the material, we use a centrifugal fan of large enough capacity to change the air or gas in the kiln many times every hour, the rate at which the fan is driven depending some the material tobe dried, but in every case the flow is rapid and positive.

The manner of charging the kiln with the ties or other articles in an upright position is highly advantageous as there are thus as few interruptions to the gas flow as possible. while at the same time practically the entire surface of the material to be dried is enveloped in the moving air and no stagnant spaces are left.

While thoroughly dried wood has little tendency to rot, because cellulose is practically insoluble in ordinary reagents, including water, and because the albuminoids, gums, and other pectous substances of the wood juices, on which fungi thrive, are rendered practically insoluble by thorough drying, we have provided,. as an additional precaution, means, such as the pipe 22, for introducing into the kiln a strong disinfectant gas such as formaldehyde, capable of certainly destroying the fungus spores or fungi remaining, within the pores of the wood.

When the ties have been thoroughly dried in the manner above specified, we apply a coating of some protective waterproofing material, such as crude petroleum, creosote oils, tar, etc, which will prevent, because of their waterproofing characteristics, the admission to the pores of the woods, of outside liquids.

We claim 1. The method of drying which c0mprises subjecting the material in a closed chamber to a substantially saturated atmosphere raised rapidly to the maximum safe temperature for the material until the material is heated throughout to that temperature, and then drying the materialby causing to flow thereover a rapid circulatmg current of air, maintaining the temperature of the air when in contact with the material at or under 160 F., while maintaining the relative humidity of the air at the point at which the moisture will evaporate from the surface of the material at substantially the same rate as-it is possible for moisture to be supplied from the interior to the surface of the material under these conditions, permitting a portion of the moisture-laden air to escape, and introducing into the circulating flow a sufficient quantity of drier air to replace the saturated air, whereby the moisture is removed continuously and uniformly and the material dried substantially without injury thereto. 2. The method of drying which comprises subjecting the material in a closed chamber to a substantially saturated atmosphere raised rapidly to the maximum safe temperature for the material until the material is heated throughout to that temperature, and then drying the material by causing to flow thereover a rapid circulating current of air, maintaining the temperature of the air when in contact with the material at or under 160 F., while maintaining the relative humidity of the air at the point at which the moisture will evaporate from the surface of the material at substantially the same rate as it is possible for moisture to be supplied from the interior to the surface of the material under these conditions,

permitting a portion of the moisture-laden air to escape, and introducing into the circulating flow a sufficient quantity of drier air to replace the saturated air, the relative humidity of the gas in contact with the material being gradually decreased until the .material is dry, whereby the moisture is removed continuously and uniformly and the material dried substantially without injury thereto.

3. In the art of. drying materials, the method which comprises causing a rapid and continuously circulating current of gas an F at maintained temperature in gradually decreasing relative humidity to flow over the material While in a closed chamber, the moisture taken up by the flowing gas being removed from the circuit by permitting a portion of the moisture-laden gas to escape and supplying to the circulating flow a sufficient quantity of drier gas to replace the exhausted moisture-laden gas.

4:. In the art of drying, the method which consists in subjecting the material to be dried to a rapid continuous flow of gas maintained when in contact With the material at the maximum permissible temperature, gradually reducing the humidity of the gas in contact With the material, and controlling the desired degree of humidity in the circulating gas by permitting some of the moistureladen gas to escape, supplying to the circuit additional heated or unheated drier air, or Whenever necessary additional Water Vapor.

5. A drying apparatus comprising a closed kiln, a drying chamber therein, a conduit connecting the upper and lower ortions of said chamber, a fan in said con uit, means for introducing into said conduit heated air and air at atmospheric temperature, heating means Within the kiln, means for Withdrawing moist air from the drying chamber and means Within the kiln for supplying a humidifying agent.

6. In the art of drying materials, the method Which comprises causing a rapid and continuously circulating current of gas at maintained temperature in gradually decreasing relative humidity to flow upwardly over the material While in a closed chamber, the moisture taken up by the flowing gas being removed from the circuit by permitting a portion of the moisture-laden gas to escape and supplying to the circulating flow a suificient quantity of drier gas to replace the exhausted moisture-laden gas.

In testimony whereof I afix my signature.

GEORGE B. MGMULLEN. GEORGE B. MCMULLEN, EARLE WV. MCMULLEN Eweeutors of the estate of George W. Me-

MuZZen, deceased. 

